BERLIN, Aug 8 (Reuters) - Rising support has drawn Germany"s Social Democrats level with the Greens and suggests their popular chancellor candidate could lead a three-way coalition government after a Sept. 26 federal election, an opinion poll showed on Sunday. The INSA poll for Bild am Sonntag put support for the Social Democratic Party (SPD) at 18%, pointing for the first time in this year"s election campaign to a majority for a three-way coalition led by the left-leaning party. The Greens were also at 18%, and the business-friendly Free Democrats (FDP) at 12%, the poll showed. Together, the three would have 48% support and a majority for a "traffic light" coalition, so-called after their respective colours, as support for other parties totalled 8%. Parties must surpass a 5% threshold to win seats in parliament. The poll put support for Chancellor Angela Merkel"s conservatives at 26%. The far-right AfD was at 11% and the leftist Linke at 7%. Merkel, in power since 2005, plans to stand down after the election. Armin Laschet, the conservative candidate to succeed Merkel as chancellor, has suffered a slump in support after he was seen laughing on a visit to a flood-stricken town. The SPD has gone on the attack, scenting a chance to win. read more The INSA poll showed that in a hypothetical direct vote for chancellor, the SPD"s candidate Olaf Scholz was well ahead, with 27% support - a five point gain from the previous week. Laschet languished on 14%, one point ahead of the Greens" candidate, Annalena Baerbock, on 13%. The Greens presented an "emergency climate protection programme" on Tuesday, aiming to reset their national election campaign after a raft of mistakes squandered their early surge in opinion polls. read more